1. Field of the Invention
The present invention relates to a telecommunications control apparatus and a method therefor, and more specifically to a telecommunications control apparatus configured to avoid the conflict of data, otherwise due to radio interference or similar cause, which are transmitted and received between a number of nodes that are spatially distributed in a sensor network, LAN (Local Area Network) or similar system or mounted on mobile bodies.
2. Description of the Prior Art
As systems for allowing a plurality of spatially distributed nodes to transmit and receive data without any conflict, available are the time division multiple access (TDMA) system and the carrier sense multiple access (CSMA) system, such as a CSMA/CA (Carrier Sense Multiple Access with Collision Avoidance) system and a CSMA/CD (Carrier Sense Multiple Access with Collision Detection) system, as taught in Y. Matsushita, et al., “Wireless LAN Architecture”, pp. 47, 53-59 and 69, Kyoritsu Shuppan Co., Ltd., Tokyo, Japan, 1996.
The TDMA system, for example, allots a particular time slot to each of a plurality of nodes so as to cause each node to transmit data only in the time slot allotted thereto, and allows the number of channels available for communication at the same time to be increased more easily than the CSMA system. When nodes expected to communicate with each other dynamically change, a certain node plays the role of a central or management node for dynamically allotting time slots to the other nodes. However, a problem with the TDMA system is that, when the central node expected to allot time slots malfunctions, the entire telecommunications system goes down.
In order to solve the above problem, there have been proposed various methods practicable without resorting to a central node, i.e., allowing the individual node to allot time slots in a distributed coordination control fashion for mutual adjustment for thereby avoiding data collisions. That is, the individual nodes interact with each other by transmitting and receiving periodic impulse signals.
More specifically, to adjust the allotment of time slots in the distributed coordination manner, each node controls, by using nonlinear oscillation, the timing for transmitting an impulse signal in response to the timing of impulse signal transmission from another node such that the impulse signal from the own node and the impulse signal from another node are spaced in timing from each other as far as possible.
Further, the methods stated above include a mode in which the interaction between the nodes is continuous in addition to the mode in which it is discrete. To implement the continuous interaction mode, as distinguished from the discrete interaction mode, phase signals are continuously transmitted and received between nodes so as to establish an adequate phase relation for thereby realizing time slot acquisition in the distribution coordination manner.
Moreover, each node generates, as the phase of a virtual node, an estimated communication timing value of another node as the phase of a virtual node on the basis of interaction using impulse and then establishes an adequate phase relation through interaction with the virtual node, also realizing time slot acquisition in the distribution coordination manner.
As stated above, the conventional methods execute timing control by relaying an impulse signal, or control message, instead of assuming two different kinds of communication ranges, i.e., a communication range and an interaction.
Although the conventional methods stated above allow communication to be efficiently held between nodes without any collision of received signals after the establishment of an adequate phase relation or conversion, the problem is that they cannot always establish a phase relation between adequate nodes and hence an adequate communication timing, depending on the characteristic of radio communication. For example, in the case of wired communication, when a plurality of nodes, sharing the same communication channels, start transmitting signals at the same time, the signals collide with each other and cause both data to disappear with the result that a receiving node cannot correctly receive data. By contrast, in the case of wireless communication, only if reception power is sufficiently great, the receiving node can receive data with great reception power even when a plurality of nodes start transmitting signals at the same time.